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Daylight savings linked to heart attacks: study

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Turning the clocks forward an hour for daylight savings may increase heart attack risk by 25 per cent the following Monday, a US study has found.

Conversely, on our side of the equator, flicking clocks back an hour this weekend will be good timing for our tickers. The research presented at the American College of Cardiology conference found that the extra hour of sleep we’ll get from switching to standard time helps lower heart attack risk by 21 per cent the following Tuesday.

The study into daylight savings and heart health examined 42,000 hospital admissions in Michigan before the start of daylight savings and the Monday immediately after, over a span of four years. It found 32 patients on average had heart attacks on any given Monday. However, on the Monday immediately after setting the time forward, there were an average of eight additional heart attacks.

The overall number of heart attacks for the full week after daylight savings didn’t change – only the number on that first Monday.

Heart attacks typically occur most often on Monday mornings, possibly due to the stress of starting a new work week and inherent changes to our sleep-wake cycle, says lead author Dr Amneet Sandhu, cardiology fellow at the University of Colorado in Denver. “Our study suggests that sudden, even small changes in sleep could have detrimental effects,” he said.

“With daylight savings time, all of this is compounded by one less hour of sleep,” Sandhu said. Previous studies have shown a link between a lack of sleep and heart attacks, but experts are still working on understaning why people are so sensitive to disturbances in sleep-wake cycles.

People who are already predisposed to heart disease may be at greater risk after the sudden time change, says Sandhu, adding that it may be beneficial to increase hospital staffing the Monday after daylight savings.

“If we can identify days when there may be surges in heart attacks, we can be ready to better care for our patients,” he said.

Researchers note the limitations to the study in that it was restricted to one state and heart attacks requiring artery-opening procedures. Sandhu says future research should compare heart attack trends in Hawaii and Arizona, which do not participate in daylight savings.


Related: How to survive daylight savings